Missing head position tracking in a 6DoF supported game?

In some games such as Microsoft Flight Simulator 2020, Elite Dangerous, and DCS World you have to use a keybinding for resetting head tracking in order for head position tracking to be enabled. This is because your initial head position needs to be calculated. 

In Tobii Game Hub, you can bind a key to Reset Head Tracking under Control Features. For games with native Tobii support such as in Microsoft Flight Simulator 2020, you can bind a key (default keybinding for this game is F12) in the settings menu for Reset Head.